Numerical analysis of vibrations of squirrel-cage induction motors based on magnetic equivalent circuits and structural finite element models

This paper presents a method for computing the magnetic forces acting on the stator of a squirrel-cage induction motor and the ensuing vibrations. For the magnetic field and force calculation, a magnetic equivalent circuit, coupled with an electrical circuit, is used. In this paper the different effects which determine the modal contents of the forces are taken into account: the spectrum of the applied voltage (in case of inverter supply), the winding arrangement, stator and rotor slotting, static and dynamic rotor eccentricity and saturation. Besides the calculation of the exciting magnetic forces, a structural analysis of an induction motor by means of the finite element method is presented. On the basis of this combined electromechanical analysis the vibrations and noise of squirrel-cage induction motors can be predicted and analysed.